This image is part of the x-ray standarization collection. In 1928, the Second International Congress of Radiology proposed the “roentgen” as the unit of quantity for expressing X-ray and gamma-ray protection. At the National Bureau of Standards, Lauriston S. Taylor’s work on the absolute measurement of X-rays, published in 1929, showed that the roentgen could be precisely measured, and resulted in the first real quantitative data on X-ray standards in this country. Working through the National Committee on Radiation Protection and Measurements (the American counterpart of the councils working on standards in Europe), Lauriston Taylor’s X-ray safety code in 1931 established guides for the shielding of operating rooms and of high voltage equipment and for protective devices for patients and operators. The initial measurements of X-rays had been made with heavy and bulky equipment. Construction in 1930 of a portable, guarded-field ionization chamber provided means for a much needed, accurate primary standard in convenient form. [From: Measures for Progress by Rexmond C. Cochrane, pp. 339-340]

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